Originally Posted by Lille-bror

Well

Nitro needs more oxygen to explode compared with methanol. An engine uses a specific amount of air at any given RPM. Now, to make the correct oxygen/fuel ratio you'll have to add much more fuel, when you run high nitro content compared to low nitro content. When you add more fuel (and oil), there will be a higher fuel flow through the engine = more lubrication. That's why you don't need the same amount of oil when you run high nitro content.